Diffusion-controlled growth of CuAl₂O₄ nanoparticles: effect of sintering and photodegradation of methyl orange

Facile synthesis of CuAl₂O₄ and sintering effects on the phase composition are reported. Annealing at 500 °C showed only CuO phase and the spinel phase started evolving at 700 °C with the concurrent decrease in the CuO phase. Diffusion-mediated growth of spinel phase was also observed at higher temperatures forming CuAl₂O₄ at 1000 °C. The material was stoichiometric and the average particle size was 55 nm, as evidenced by EDS and FE-SEM studies, respectively. The zeta potential of +30 mV and lower (0.346) value of the poly dispersive index (PDI), confirmed the high dispersability of CuAl₂O₄ in water. The favourable band gap (2.2 eV) makes it suitable as visible light photocatalyst. Owing to its positive surface charge and conducive pH, material could adsorb anionic methyl orange dye. A total of 74% of the dye could be recovered by a simple methanolic extraction. The visible light photocatalysis of the same dye leads to 67% decolouration and the addition of H₂O₂ accelerated the photodegradation to completion. The catalyst displayed excellent reusability and stability even after five successive runs.